This application claims priority from German Patent Application No. DE 10115512.3, filed Mar. 28, 2001, incorporated herein by reference.
The invention relates to a collision damping arrangement for motor vehicles for absorbing energy in a collision of a motor vehicle with an obstacle.
Collision damping arrangements of the type herein are used for the protection of passengers of a motor vehicle during a collision, including head-on, rear end, and side collision. Energy released by the collision is absorbed and transferred to the passenger compartment in reduced form, or not at all. Such collision damping arrangements typically include a crashbox damping member between a bumper member and damping longitudinal members. The longitudinal members are connected to the passenger compartment and longitudinally absorb energy. The bumper member is typically a bumper-side cross member, the so-called bumper cross member, and extends perpendicularly to the longitudinal members. The crashbox damper member is located between the bumper and the longitudinal member and is longitudinally deformably compressible in response to longitudinal force application, to absorb collision energy, particularly at low speed, without deformation of the longitudinal member, to minimize frequency of replacement of the latter, which is expensive. The present invention is directed to improvements in the noted intermediate crashbox damper member.
As is known in the art, an important task of the bumper cross member during a collision is to ensure a tensile connection between the right and left side of the vehicle body in order to provide the best possible protection for the passengers. The collision damping arrangement provided by crashbox damper members between the longitudinal members and the bumper cross members must therefore realize a connection between the pertinent members with sufficient tensile strength as well as the desired energy absorption by means of deformation. The requirements regarding the material and design of such collision damping arrangements are therefore considerable. Such collision damping arrangements are typically made of metal, such as steel, aluminum, magnesium, or suitable alloys. Different types of steel, including high tensile steel appropriately formed, are often used. Automotive collision damping arrangements for energy absorption can also be used for side collisions, within structures generally referred to as side impact systems, for example where the bumper is in a door side panel. The area of the automotive B column and possibly the C column could be of interest with regard to arranging the collision damping arrangement. Collision damping arrangements of the present type can also be used inside the passenger compartment, for example as support arrangements for kneepads.
The function and effect of a collision damping arrangement is primarily determined by the course of the force path, wherein considerable significance is attributed to the onset of the deformation. Complex movements of the bumper occur in particular in the case of a laterally shifted head-on collision which the design of the collision damping arrangement must taken into account. If the mounting surfaces in the arrangement are arranged parallel to one another, then the adaptation to the complex arched course of the bumper cross member or strake must be accomplished in another way. A known solution is to include bumper cross members having various cross-sections or wedge/arch-shaped compensating elements inserted between the bumper cross member and the collision damper member and then welded or bolted, for example EP 0718157A1, EP 0718158A1. It is also known to provide a collision damping arrangement in which the mounting surface for the bumper cross member and the mounting surface for the vehicle longitudinal member are not arranged parallel to each other, but at an acute angle, for example 15xc2x0, DE 19829566A1. This design accounts for the strake in the collision damper itself.
It is also known to hinge a collision damper to the bumper cross member by means of a pin bearing, DE 19832114A1. This solution has the advantage that the angle between the bumper cross member and the front head side of the collision damper does not need to be determined in advance, and may also change in the event of a collision, without the connection between the bumper cross member and the collision damper being severed. However, such a pin bearing presents problems with regard to the technology of the connection and the rigidity of the bumper cross member. In addition, the force conductance by means of the pins into the collision damper is not optimal.
The angle between the bumper cross member and the head surface of the collision damper changes in the case of a laterally shifted head-on collision because the bumper cross member is first pushed in strongly in the center, and only then an essentially uniform deformation across the full width of the hit area in the longitudinal direction follows. In the case of known collision dampers, it may happen that the force component perpendicular to the longitudinal direction, or other lateral force component, is so large at the very onset of the head-on collision that the bumper cross member is severed from the collision damper or that the collision damper gives way laterally. If this occurs, the collision damper loses its effect already at the onset of the head-on collision, an effect which should only begin afterwards for the protection of the passenger compartment.
The present invention provides an automotive collision damping arrangement which is optimized with regard to its characteristics in the case of a collision, including in the case of a laterally shifted head-on collision.
In one aspect of the invention, in particular in the case of a laterally shifted head-on collision, the bumper cross member, arched in accordance with the strake, is selectively deformed in the longitudinal direction on the side facing the inner side of the vehicle body, where the force is applied first or is strongest at the onset, without the main part of the crashbox damper member being deformed at this time. The preliminary path realized according to the invention ensures that in the case of a laterally shifted head-on collision, the forward mounting surface of the crashbox damper member initially arranged at an acute angle to the rear mounting surface lines up parallel or approximately parallel to the lead mounting surface. At the onset of deformation, the collision damping arrangement remains intact, and its deformation in the longitudinal direction for the purpose of energy absorption starts only after the bumper cross member has been considerably deformed toward the inside in the particularly vulnerable area towards the center of the vehicle body. The function of the crashbox collision damper is retained even in the case of a laterally shifted head-on collision, and the passenger compartment remains optimally protected.
In a coordinated alternative of the doctrine of the invention, the forward mounting surface of the crashbox damper member on the bumper cross member is shaped so that the opposing facing surface on the bumper cross member can be arranged at a considerable angle range without problem. Instead of a pin bearing used in the prior art, a bearing based on a cap in the form of a spherical segment or arch in a similar fashion is used. The bumper cross member may be axially bolted or welded without problem. The base of the cap in the transition to the remainder of the crashbox damper member aft thereof is a fold which permits asymmetrical buckling, with the remainder of the crashbox damper member aft thereof remaining intact at initial force application in the case of a laterally shifted head-on collision in a similar fashion as noted above. The result of this asymmetrical buckling or sinking of the cap into the body of the hollow crashbox damper member is that the fixed connection between the bumper cross member and the crashbox damper member is not severed, but instead is retained even in the case of a laterally shifted head-on collision.